From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753880AbbHDVcN (ORCPT ); Tue, 4 Aug 2015 17:32:13 -0400 Received: from mail-pa0-f41.google.com ([209.85.220.41]:36149 "EHLO mail-pa0-f41.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752573AbbHDVcL (ORCPT ); Tue, 4 Aug 2015 17:32:11 -0400 From: Matt Turner To: linux-alpha@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Richard Henderson , Ivan Kokshaysky , Matt Turner Subject: [PATCH] alpha: select CONFIG_ARCH_USE_CMPXCHG_LOCKREF. Date: Tue, 4 Aug 2015 14:35:05 -0700 Message-Id: <1438724105-26892-1-git-send-email-mattst88@gmail.com> X-Mailer: git-send-email 2.3.6 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Alpha we have spinlocks that are 32b in size and an efficient cmpxchg64 implementation, so we qualify to make use of cmpxchg backed lockrefs. Select the ARCH_USE_CMPXCHG_LOCKREF Kconfig symbol and provide a trivial implementation of arch_spin_value_unlocked to satisfy the lockref code. Using Linus' simple testcase from http://article.gmane.org/gmane.linux.file-systems/77466 on a dual CPU ES47 system I see around an 8% gain: N Min Max Median Avg Stddev x 30 6194580 6295654 6272504 6272514 17694.232 + 30 6731164 6786334 6767982 6764274 13738.863 Difference at 95.0% confidence 491760 +/- 8188.17 7.83992% +/- 0.130541% (Student's t, pooled s = 15840.5) Signed-off-by: Matt Turner --- arch/alpha/Kconfig | 1 + arch/alpha/include/asm/spinlock.h | 5 +++++ 2 files changed, 6 insertions(+) diff --git a/arch/alpha/Kconfig b/arch/alpha/Kconfig index bf9e9d3..f515a4d 100644 --- a/arch/alpha/Kconfig +++ b/arch/alpha/Kconfig @@ -3,6 +3,7 @@ config ALPHA default y select ARCH_MIGHT_HAVE_PC_PARPORT select ARCH_MIGHT_HAVE_PC_SERIO + select ARCH_USE_CMPXCHG_LOCKREF select HAVE_AOUT select HAVE_IDE select HAVE_OPROFILE diff --git a/arch/alpha/include/asm/spinlock.h b/arch/alpha/include/asm/spinlock.h index 37b570d..fed9c6f 100644 --- a/arch/alpha/include/asm/spinlock.h +++ b/arch/alpha/include/asm/spinlock.h @@ -16,6 +16,11 @@ #define arch_spin_unlock_wait(x) \ do { cpu_relax(); } while ((x)->lock) +static inline int arch_spin_value_unlocked(arch_spinlock_t lock) +{ + return lock.lock == 0; +} + static inline void arch_spin_unlock(arch_spinlock_t * lock) { mb(); -- 2.3.6